17 children in Spain developed hypertrichosis, which causes excessive hair growth, after ingesting the wrong prescribed drug. (Photo: Getty Images)

Parents are anguished by a medical mistake that caused “werewolf syndrome” in their children, leaving their bodies covered with hair.

In Spain, 17 children developed a condition called hypertrichosis, which causes excessive body hair, when they ingested minoxidil, a prescription hair-growth drug, instead of omeprazole, one for heartburn and reflux disease.

According to The Guardian, Spanish minister of health Maria Luisa Carcedo said a laboratory “put this medication [minoxidil] in a container that was marked omeprazole” unbeknownst to pharmacies that dispensed it.

“The original shipment of bulk omeprazole from India was analyzed and the results showed that it was in perfect condition,” a representative of the Spanish Agency of Medicines and Medical Devices (AEMPS) told the Spanish newspaper El País. “The problem was when it was divided into small batches that were later also sold in bulk. There was a serious confusion in the process. It’s not that omeprazole was mixed with minoxidil [a medication to treat male-pattern hair loss], but rather that the package leaflet said one thing and the pharmacy another.”

The Malaga-based pharmacy, FarmaQuimica Sur, did not respond to Yahoo Lifestyle’s request for comment. But the New York Times reports that the medicine was removed from circulation and the laboratory closed. The lab reportedly has six months to provide answers into the mix-up.

One mother, Ángela Selles, told El País that her son Uriel started growing body hair at 6-months-old. “My son’s forehead, cheeks, arms and legs, hands became covered in hair … He had the eyebrows of an adult. It was very scary because we didn’t know what was happening to him.”

Selles’ son drank almost three bottles of the liquid medicine, leaving his liver “not great,” she told the paper, adding that doctors have assured her he will recuperate.

A second mother from the capital city told El País that her 3-month-old son inexplicably grew body hair, describing the “anguish of going from one doctor to another,” who surmised the issue was either metabolic or genetic.

The syndrome, which affects both men and women, is rare: There are less than 100 cases around the world. It can develop in three ways. The first cause is genetic — a 2011 study published in the American Journal of Human Genetics found that an additional X chromosome can activate a gene called SOX3, per LiveScience, resulting in hair growth.

Another factor, according to Guanche, are hormonal imbalances, such as adrenal and pituitary disorders that cause an excess of testosterone. The eating disorders anorexia nervosa and bulimia, which alter the body’s metabolism, and drugs such as immunosuppressants and hair-growth drugs — what occurred in the Spain — are also causes, according to Medical News Today.

Depending on the type of hypertrichosis, hair removal, whether through electrolysis, shaving, waxing, plucking, or laser surgery, can be fruitless.

“If the condition is congenital, it’s much harder to remove hair,” says Guanche. “Laser is one method, but it’s extremely expensive, requires multiple sessions, and isn’t available in some countries.” Even so, in congenital cases, treatment is only temporary.

According to the New York Times, Spanish dermatologists say the children’s overgrowth should fall out within three months of ceasing the drug. Although, it reports, a 2-year-old girl who still has body hair, stopped taking the medicine back in May.